When locking bicycles and other portable objects to fixed objects in an attempt to prevent theft, several locking devices have been used, the most common of which is a length of chain and a commercial padlock. Both the chain and the padlock are made of hardened metal to resist cutting or other means of destruction. The padlock shackle is normally similar to that of the chain so that they both will resist an equal amount of destruction. As a result of their similarity in characteristics, the size of the shackle of the lock is such that it cannot pass through a normal link of the chain. To overcome this problem and still use the proper padlock, the chain is provided with one or more larger links, large enough to allow the passage of the padlock shackle.
In use, the chain is normally passed around or through the bicycle or article to be secured and around a hitching post or other fixed object. The padlock shackle is then passed through the larger links and locked. With this manner of attachment, there will often be a large degree of slack allowing relative movement between the article and the object to which it is secured. Where this slack exists, the chain may be more vulnerable to unauthorized removal than if it were maintained in a taut condition.
Slack chains can also permit damage to the secured article and this is particularly problemsome where a chain is used as a safety chain with a towed vehicle. When using a trailer hitch or other towing means for towing a trailer, a safety chain is used to prevent disconnection if the hitch fails. The safety chain must normally be maintained in a slack or loose disposition due to its construction. Because of this, the towed vehicle may swing wildly behind the towing vehicle if the main hitch fails; and this will present a dangerous situation to other traffic on the highway.